In the following description, the biasing means will be referred to as a spring. This is simply for convenience of description and is to be understood as not limiting the type of biasing means to be chosen.
Preferably a flat card will be mounted on each side of the spring, so that the card lies in a plane at right angles to the direction of expansion. The spring will preferably be attached to the card on each side: for example, two projections on each end of the spring engage in corresponding holes in the cards in order to maintain the spring in the correct position. The cards obviously should be of smaller dimensions than the internal dimensions of the bag, so that they can be inserted and the bag closed. The cards may, in fact, be considerably smaller than the bag, and a limited range of card sizes may be used over a large range of bag sizes. The cards need not be the same size on opposite sides of the spring. The larger card would then locate the spring in the correct position in the bag and the smaller card would provide a contact area for pushing a side of the bag outwards.
The releasing member may be a pin inserted in the coils of the spring, if a helical spring is used, or could be a pin engaging a tie-piece extending from the card on one side of the spring to the card on the other side. If such a pin is used, a thread is preferably attached to one end of the pin and this thread is led out of one corner of the bag so that the pin can be released without opening the bag. If the bag is itself contained in a protective polythene bag, the thread can extend out of this bag too, so that no unwrapping would be needed.
It is advantageous if the movement of the releasing member required to release the spring is at right angles to the direction of expansion of the spring (i.e. parallel to the cards, if these are used). This makes it possible to operate the device to expand the bag, without opening the bag.
The invention also extends to a method of packing bags, wherein the bags each have inserted in them a biasing means, and the bags are then compressed as they are packed into a container, so that the biasing means is compressed and the bags occupy little space.
It is already known to pack bags with foam rubber or other inserts. Although such a method might fall within the terms of the definition above, they do not satisfactorily perform the same object, and so it is envisaged that the present invention should be restricted to biasing means which have an expanded size which is say at least five times the compressed size.
In a preferred method however, the biasing means are compressed and held compressed by a separate member before being inserted in the bags. No compression is then necessary when the bags are actually packed in their container.
Preferably the device is inserted in such a way that the member holding the biasing means compressed can be released without opening the bag.